Furnace and method of operating the same



De@ 3l, 1929. E. H. swlNnELL ET AL FURNACE AND METHOD OF OPERATING THE SAME Filed Jan. 29, 1925 4 Sheets-Sheet 1 A, m Ns: -|||-1. :--|-||--I--I 3. 3 -j m /f//f/ y A ///f/// L? IL N N IIYINNN mv lNNl ,A A w T Q SN' g www T I Hm Q H HHHWU A I" m Mw l wv Dec. 3l, |929. E. H. swlNDELI. ET AL rUnNAcE' AND METHOD 0F OPERATING THE SAME 4 Sheets-Sheet 2 Filed Jan. 29 1923 De- 31, 1929. E. H. swlNDl-:LL E-r AL 1,741,209

FURNACE AND METHOD OF OPERATING THE SAIE Filed Jan. 29, 1923 4 Sheets-Sheet 3 INVENTORS Dec. 3l, 1929. E. H. swlNDELL ET AL FURNACE AND METHOD OF OPERATING THE SAME Filed Jan. 29. 1923 4 Sheets-Sheet 4 f /f/ //////////////////f//f/f l 5 R o l ,f/ l ,T f N f f f E f f V W i N f l, f f f f l l f f l f f l f f l f l l f f f the annealing boxes.

Patented Bec. 3l, QZ

narra/a ,stares TENT FFiC EDWARD H. SWINDEJL AND FRANK W. BROOKE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNQRS T0 VTILLIAIJI SWINDELL & BROS., OF PITTSBURGH, PENNSYLVANIA, A.

con-renderen or PENNSYLVANIA FURNAGE AND METHOD OIF OPERATING THE SAME Application alsa January 29, 192s. seria; No. 615,511.

The present invention relates broadly to furnaces and the method of operating-the same, `and more particularly to heating or annealing furnaces.

At the present time, it is customary to construct heating or annealing furnaces for straight combustion closed annealing, for electric open annealing and for continuous annealing.

Straight combustion closed annealing is objectionable to some extent by reason of the lack of uniformi-ty of temperature Withinv the furnace thereby affecting the uniformity of the product, and by reason of the warping of I For this reason, it is being gradually replaced by electric open annealing. Due, however,A to the comparatirely high cost of electric current, such furnaces have been largely confined to the treat-ment of special sheets and compositions inv connection with which absolute uniformity is essential. With continuous vannealing-furnaces, there is obtained continuous operation, rouille firing at an economlcal rate, partial jcooling of the annealed material within the furnace and preheating of the.

In furnaces of this latter Y cunibustion air.v type as now constructed, it 'is customary to load the cars at one end and unload themat the opposite end, ears are 4returlied outside the furnace, thereby .wasting a considerable portion of their sen'` sihle'heat. W here the empty cars have been returned through the furnace, the heat of the material unloaded at the discharge end is lost, iVhere the cars have been passed in opposite directions through the furnace in such manner that the heated or outgoing cars radiatevheat to the cold or'incomingcars. two operating stations at opposite ends ofthe furnace have been required for loadingand unloading. Furthermore, the construction has not been such. vas to secure high thermal efficiency.

B v the present invention there is provided an improved construction which combines certain Ot the advantageous features of the previous t ypcs of furnaces referred to herein '1 n such manner that high thermal etiicicncy is obtained together with uniformity of In some cases the empty'A temperature and 'simplicity of operation witha minimum amount of scaling and warping.

In the accompanying drawings, there are illustrated certainpreferred embodiments of the present invention, the drawings being largely diagrammatic as they do not define the limits ol. our invention, it being contemplated that changes may be made in the construction and operation disclosed herein without departing fron'i'thespirit of the invention or scope of our broader claims.` A

In "the drawings, Figure 1 is a horizontal sectional View through a. furnace constructed in accordance with'the present invention and diagrammatically illustrating the construction and operation thereof;

the line Il-II of Figure 1;

Figure 3 F igure 2 is a transversesectionl view on 1s a transverse sectional View on the line III-III of Figure l;

Figure 4 is a sectional view corresponding to4 Figure 3, and illustrating a slightly modifiedl form of furnace;

Figure 5 is a. sectional view, corresponding to Figure 2, of a furnace of the type partly illustrated in Figure 4; and

Figure 6 is a diagrammatic crosssectional view of a modified form of'furnace.

The present. invention provides a furnace in which a maximum saving of heat is effected and in which the advantages both of a combustion furnace, due to its low-operating cost, andA of an electric furnacc,-due to its uniformity of temperature, are combined. One method of obtaining the desiredresults is illustrated in Figures l, 2 and 3 in which there is shown a'furnace 2 having' its walls,

roof and foundation of any suitablemate" rial. At the charging end of the furnace there is provided a charging chamber 3 havting a chargcdcar to be moved either later-` nally therethrough.

A charged car is adapted to be fed from the charging chamber, 3 into the prcheating chamber 6. Withinthis chamber there may be arranged any desired number of tracks, three sets being illustrated in this particular allv from the charging opening or longitudi-- These furnaces maybe `of anyvwell knownV construction, but vmay AAadvantageously be' form. The entering car is adapted to be laced on either of the outside pairs of tracks. ommunication between the charging chamber 3 and the preheating chamber 6 may be cut off at will be a suitable system of doors 7,

as is customary in this art.

Within the preheating chamber 6 theenterlng material is subjected tothe heat given off previously heated material and the carri'ers as will be more fully pointed out hereinafter. VThis material is then adapted to pass from the preheating chamber 6- into one orthe other Vof the -independent furnaces 8;

heated b regenerative principles of the t pe shown, or example, in ASwindell Patent o.

624,401of May 2, v1899. AVi-lila traveling throu h the furnaces, -thete'm'peiatureof the cars, t e material thereon, and the annealing boxes, is brou ht to approximately the desi'red point. t` this temperature the material may leave the combustion furnaces, passing outwardly therefrom -int-o av transfer chamber 9. Within this chamber, thelcars are moved laterally onto a-central track and may then be passed intoan electrically heated furnace 10. Thisfurnace is illustrated as having electrical heating' elements 411 adjaf'cent each side Vthereof although it will. be apparent that the arrangement ofthe heating elements and the construction thereof may be varied-in accordance withfthe requirements of the particular lfurnacebeing installed..

' While the specific arrangement ofthe com; bustio'n and the electrically heated 'furnaces is immaterial, it hasl been found verydesirable to .arrange the same in' sideby-side relationship .whereby there is'av common wall between the respective chambers. y In this man-.

ner the comparatively. inexpensive fuel utilized for maintaining'- the temperaturewithin the combustion furnacesis effective for assistingin the maintenance ofthe -temperature within thefurnface'l'O. In accordance with 4the best. practice, the temperature within the furnace 10 is preferably maintained as nearly uniform as possible.V In this manner uni forni. results may be obtained. It will be a parent that by utilizingr electricity as t 1e heatingmeans, such a' control is easily and automatically effected. When an electric furnace is holding its temperature constant, the consumption of ,power during the period of operation represents the heat loss throughthe of heat and therefore no expenditure ef ower. The walls 12 intermediate the comustion furnaces 8 and the furnace 10 are 11.1

rectl subjected to theA temperature -jwithin the urnaces 8 and thereby the temperature difference on opposite. sides of .this lining is kept at a minimum.- In order'tol'ninirnize heat losses through the roof 13, there may be' provided any desired amount ofinsulating covering 14. .lhis arrangement therefore provides for accurate and automatic temperature'control within'the chamber ltog'ether with an ideal atmospheric 4condition-thereinl both of which are obtained at anabsolute u minimum expenditure o f power.'- y

The substantiallyuniform powerjconsump-'j tionwithin. the' furnace 10 is also v er'y desir-1. able when .it is considered that the chargetfor j electricity isconsiderably decreasedfwh'ere' a,

constant load factor is maintained.' jf

After the materialhas v4subjected within the-furnace lQtothede. ature for the'requiredlngth--off pass outwardly therefrom on, i he. ent

Vithin this chamber, as cleal own .by

al track within the preheatingchaxnb'er "6.--

Figure 3, there arefno interme Iat'efl'ongji-@ tudinally extending partitions.

"I'Thefheat `1 from the ear and its charge Vis thereforeper#.. mitted to `radiate freely in siibstantially' to commercially effect any material saving;

the amountloff'radiation-in thisA direction@v may be minimized .by'theprovision of 'sand seals 15, asis customary in the` art. The

heat radiatedflaterallyis directly absorbed -rfby. the incoming zc ars on the outertracks, while the heat v'nadiated 'f upwrdly may be" turn may supp yfth ombiigti furnaces 8.whe rebyp and a considerable' sa With certain classes sirable that the *perio required"- for bringing herebyfeffected;V

the incoming material to thefdesired temmaterial, it is de ilo perature should befslub's'tantially ltwice as long as the period r q1`1ii ed {ontheactual heat treat-ing operation. Thus, for example,

if the material leaves the" preheating chamher at a temperature o f -40 0" ".F- .,20 hours may be .necessaryfto Araise the temperatureA to the desired point, say-'1 5 5 0'F. within the furnaces 8. Within the-"furnace'O' 'there' will be maintained 'a temperature of 1550 F., but it will only-be'nengssary to keepthe material withinA this furnace for'4 approxi-v mately ten hours. 'As there are'two tracksv supplying material tothe furnace 10, it. will be apparentrth'at thej-travelthrough'this furnace is twiceas fast as the travel' through the furnaces 8, 'thereby auton'latically providing the desired time intervalsi It will be understood that the preheating chamber and the furnaces 8 and 10, respectively, may be separated -by movable closures 116 of any desired construction, and that the transfer chamber 9 may in turn be separated from the furnaces by movable closures 117 The closures 117 are Very desirable in that they prevent the passage of any considerable amount of sulphur from the combustion furnaces into the electric furnace 10. This increases the length of life of the electric heating elements, as they are thus in effect protected from the action of the sulphur.

It will be understood that if it were desirable to shorten the combustion heating period and lengthen the electric maintaining period, the central furnace could be heated by combustion and the two outer furnaces could be heated electrically. The material would then be fed into the central furnace and thence into either of the two" side furnaces. Also, if it is desired to provide uniform periods of heating and electric maintaining, the operation may be carried out by the use of equal numbers of combustion furnaces and electric furnaces.

In Figures 4 and 5 there are illustrated transverse sectional views through a modified form of installation having outside combustion furnaces 8', each with a single pair of tracks and a central electrically heated furnace 10 with two airs of tracks. In operating this installation, it will be apparent that the electric maintaining and heating periods are of the same length, as each combustion furnace 8 may supply a single track within the furnace 10. On the other hand, a single combustion furnace 8 might be utilized in some cases for keeping both cl the tracks within the furnace lOilled. This operation would provide a heat maintaining period substantially t'wice as long as the heating period.

In an installation of this character, the preheating chamber 6 preferably has 'in addition to the air pipes 16, pipes 17 adapted to lie between the cars on the center tracks. In this manner, the radiated heat from between the cars is utilized for preheatlng the air. These air pipes may supply air through suitable connections, 'not shown, to the air intakes 18 Vfor the regenerative combustion system. This regenerative system is here illustrated as of i type shown in the Swindell patent be referred to, although ythis construction illustrative only.

The preheating chamber not only serves to reclaim the heat radiated from the neat treated material in three different directions, but also serves the purpose ot' filing the material to a temperature at wint" be exposed to the atmosphere. y

Unless it is desired to load the cars ilirectly at the rolling mill, the sensible heat of the cars and covers may always be reclaimed by immediately removing the treated Work from the outcoming cars, reloading the cars and immediately charging the same back into the preheating chamber.

In some instances, it may be desirable to cover the annealing boxes and the cars with a high carbon pitch. As the volatile portions of the pitch burn out, there is left a heavy sooty deposit. This deposit in some instances has the effect of cutting down scaling and warping of the cars and the annealing boxes. Also, the burning pitch generates a considerable amount of heat which would be retained to a large extent by the cars and the annealing boxes.

In Figure 6 there is shown an installation comprising independent furnaces 21, QQ and 23. (jet-tain of these furnaces may bc of the combustion type, as, for example, furnaces 21 and Q3; while the remaining furnace may be electrically heated. lVith this arrangement, the combustion furnaces 2l and 2:3 would tend lto maintain a high heat in the common furnace walls .24 and 25, thereby (lccreasing to a minimum the temperature dil"- lcrencc on opposite sides of these -walls. order to secure a substantially similar result with the top wall 26, there may be provided a supplemental roo l 27 providing a chamlm' :38. This chamber, in order to 'secure the desired circulation ot' heat within the combustion furnaces, may have ported partition walls 29. By such a construction the combustion furnaces substantiall).v enclose. and thereby materially restrict radiation ot heat from, the electric furnace or furnaces. This principle is applicable to all o the various forms of installations disclosed herein.

The advantages oi' vthe present invention arise from the provision ol an improved iustallation and a method of opifrating the sama-whereby it is possible to utilize both inexpensive and comparatively expensive fuels at a minimum of c:

Further advanagi ar e from the simplicity of operation :at ic ambition, the drcreased aling and warping the :murat ing box of material to be treated. part ly diie brought to he fact that they are grad...

thermal up to tig-orginalure. and tbc ciiicicucy of tbc instfiliationr 1We claim l. ln c. mi lzod ci" annealing, the steps consisting in iirst heating the shapes to be auncaled in a chamber hculcd bj.7 combustion, corivcyingg; said shapes out of .said chamber. transferring the shapes la "2 into a secon-fl chamber chti, and further healiw; said si' ond chamber.

In a metboii f i g r sisting in first hcatu shapes to bo :innealed in a chamber heated by combustion,

s'f. the #cpa on 

